That sound you hear may be the sputtering of Wisconsin Democrats and public-sector unions’ campaign to oust Republican Gov. Scott Walker. On Tuesday, Democrats went to the polls to choose a candidate to square off against Walker in next month’s recall election. But the union-led opposition’s hopes that the standard bearer would be a Big Labor darling were dashed with the election of Milwaukee Mayor Tom Barrett, rather than the unions’ preferred candidate, Democratic operative Kathleen Falk. Falk’s defeat marks only the latest setback for a recall campaign that is increasingly running out of steam.

The differences between Barrett and Falk are small but politically significant. Though they both pledged to eliminate Walker’s restrictions on collective bargaining for most state workers, they disagreed on the methods. Falk took the more union-friendly approach, assuring her supporters that she would veto any budget that didn’t restore collective bargaining. That promise earned her the endorsements of the state’s leading public-sector unions, including the state chapter of the AFL-CIO and the Wisconsin Education Association Council, the state’s biggest teachers union.

Barrett refused to go as far as Falk. While he is also committed to restoring collective bargaining, he has said that he would do so by introducing the issue in a special legislative session. The latter is particularly unattractive to unions because it would require Republican support for the legislation. Barrett’s victory in the Tuesday primary means the unions’ dreams of restoring collective bargaining through gubernatorial fiat have been shattered.

Yet another setback for the unions is that their efforts to turn the recall into a referendum on collective bargaining appear to have failed. While union activists and organizers still see collective bargaining as the dominant recall issue, Wisconsin’s voters, among them many Democratic primary voters, disagree. Polling of primary voters conducted by Marquette University found that over half of those who voted in Tuesday’s primary favored Barrett’s compromise-seeking approach on collective bargaining over Falk’s and the unions’ demands that it be reinstated without debate. Collective bargaining has also faded as a galvanizing issue. Increasingly, the recall has come to resemble a general election, where the main focus is on standard issues like jobs and unemployment. Doom-saying from Democrats and their union allies notwithstanding, challenging the unions over collective bargaining has not fatally diminished Walker’s political prospects.

If all this weren’t bad enough, there are also growing divisions in the state left’s ranks. Those divisions came to the fore this week with news that the Wisconsin Democratic Party was canceling a “unity rally” this Wednesday in the state capitol to support the winner of the Democratic primary and to bring together Barrett and Falk’s respective supporters. It was not to be. Barrett declined to attend the rally, fueling rumors that he didn’t want images of him commingling with union organizers to be used against him by Walker. Still others speculated that the cancelation was a dirty trick by Falk intended to make embarrass Barrett. Whatever the explanation, this was not the kind of infighting that Democrats and unions had anticipated when they made Walker their target.

None of this might matter if Barrett where a shoo-in to defeat Walker next month, but he isn’t. Barrett has already lost to Walker in 2010, when he was his challenger for governor. That high-profile race gave him the statewide name recognition and clout to beat Falk, but Walker is a different proposition altogether. Still, the race will be close. Polls show the two are in a statistical tie with weeks to go.

That bad news for Barrett is that his path to victory is far from clear. Democrats’ original intent had been to use Walker’s budget reforms – most notably the restrictions on collective bargaining and some cuts in state aid – against him. Unfortunately for this strategy, collective bargaining is not the hot-button for most voters that it is for union and left-wing activists. Meanwhile, Walker’s cuts in state aid, forced by the state’s yawning $3.6 billion deficit, have not hit nearly as hard as Democratic talking points suggest.

That is in large part because of something Democrats and unions cannot bring themselves to admit: Slowly but surely, Walker’s reforms have been working. Walker’s restrictions on collective bargaining, for instance, have allowed Wisconsin’s school districts to generate substantial savings, and thereby to avoid the massive layoffs that teachers unions claimed were inevitable. Nor have Walker’s budget cuts brought the state to its knees, as Barrett knows. Last year, he charged that Walker’s cuts would make Milwaukee’s deficit “explode.” Instead, Walker’s curbs on collective bargaining contributed to the city posting an $11 million net gain in its 2012 budget. The only explosion was of the egg on Barrett’s face.

One area where Walker remains vulnerable is jobs, of which the state has produced fewer than Walker promised. But on this issue, too, Walker has a case to make. After hemorrhaging months for the past year, Wisconsin has begun gaining jobs recently and the state’s unemployment is now at its lowest point since 2008. And while Walker remains a polarizing figure in the state, polls show that Wisconsinites believe his reforms have made it more hospitable to businesses and job creation. In a recall that has deeply divided the state, that is a positive message to take into election day.

Needless to say, this is not where Walker’s opposition expected to be at this point in the recall. Goaded on by a friendly media, they believed their own hype that Walker was a “dead man walking,” as a Time magazine article dubbed him. But as the recall effort founders amidst internal feuding and a loss of enthusiasm for the unions’ agenda, it may well be that Walker will be the one who lives to tell this tale.